2,5-Dihydrofurans, 2,5-dihydrothiophenes, and 2,5-dihydro-1H-pyrroles (3-pyrrolines) are building blocks for the pharmaceutical and commodity chemical industry. 2,5-Dihydrofurans are reduced to tetrahydrofurans. 2,5-Dihydrothiophenes are reduced to tetrahydrothiophenes or oxidized to thiophenes. 2,5-Dihydro-1H-pyrroles are reduced to pyrrolidines. Tetrahydrofuran is a chemical of commerce and a common organic solvent. A number of substituted tetrahydrofuran derivatives are also produced in great quantities for use as solvents, polymer building blocks and for various other purposes. Tetrahydrofurans are also useful as starting materials for synthesis of polyether polyols. 3-Methyltetrahydrofuran is an important building block for production of elastomers and is used as a solvent when a higher boiling point than that of tetrahydrofuran is necessary. 2-Methyltetrahydrofuran is a replacement solvent for dichloromethane and is a superior solvent for performing Grignard reactions as well as a cleaner burning co-solvent for spark ignition motorfuel. Tetrahydrothiophenes are useful as antimycotic agents, and as odorants in natural gas. Tetrahydrothiophene is useful as an intermediate in the production of the solvent sulfolane (produced by oxidation of tetrahydrothiophene). Thiophene is a decomposition product of tetrahydrothiophene. Thiophenes are recurring building blocks in organic chemistry with applications in pharmaceuticals. 3-Alkyl and 3-arylthiophenes are important building blocks for conductive polymers. The pyrrolidine ring structures are found in many pharmaceutical drugs such as procyclidine, enalapril, clindamycin, hyoscyamine, fosinopril, altace, combivent and kytril. A pyrrolidine ring is the central structure of the amino acids proline and hydroxyproline. Pyrrolidines are also useful to treat hormone refractory prostate cancer and as antipsychotic and analgesic agents.